Loss of functional small bowel surface area following surgical resection for disorders including Crohn's disease, ischemia, trauma, or radiation enteritis may result in short bowel syndrome (SBS), an important cause of morbidity, mortality and health care costs in the U.S. SBS patients are frequently dependent on parenteral nutrition to meet their nutritional requirements. Following intestinal resection, the remaining small bowel epithelium mounts an adaptive response that increases villus height, crypt depth and enhances nutrient and electrolyte absorption. However, the adaptive response in humans is unpredictable and it may require up to two years to determine which patients will wean off parenteral nutrition, even with an accurate assessment of remnant small bowel length. The mechanistic basis for this clinical variability is unknown. Our application seeks to explore new regenerative, therapeutic approaches to enhance small bowel functional surface area, using patient biopsies from the PI's large SBS patient population. Our approach will translate observations from our preclinical models of short bowel syndrome and myofibroblast signaling in the stem cell niche into studies in human SBS that have therapeutic potential. We have shown that a myofibroblast protein, epimorphin (Epim) regulates crypt fission, gut epithelial proliferation and myofibroblast secretory function in mice. Co-culture with Epim-/- myofibroblasts further enhances WT mouse crypt enteroid growth and surface area. Our overarching goals are to enhance the proliferative epithelial response and increase small bowel surface area as a therapeutic strategy for SBS. Our overarching hypothesis is that modulating myofibroblast Epim and its targets will enhance human small bowel growth providing a novel regenerative therapeutic approach to SBS. Aim 1 will directly translate our mouse studies by establishing stem cell/enteroid and myofibroblast cultures from the PI's large cohort of SBS patients. We will address the hypothesis that co- culture with Epim-deficient myofibroblasts increases the growth of human enteroids. We will determine whether growth and proliferative capacity of enteroids in vitro can predict the ability t adapt and wean from parenteral nutrition. Aim 2 will address two hypotheses. 1. MF-crypt epithelial interactions are modulated by Epim deletion to increase crypt stem cell proliferation and enteroid growth via altered Bmp, Hh, and Wnt signaling pathways. 2. Epim demonstrates context-specific inhibitory vs. pro-exocytotic roles in regulating MF secretion. Our studies are significant because we will directly translate our findings from preclinical studies to human studies of Epim deletion's effects on MF function in the stem cell niche. We will expand our unique clinical collection of small bowel crypt stem/enteroid cultures from SBS patients, and generate a national resource for potential future high throughput screening of therapeutic agents that enhance stem and crypt cell proliferation in SBS. Epim and the secretion of soluble factors that are modulated by Epim deletion represent potential novel therapeutic targets to promote intestinal stem/crypt epithelial proliferation, leading to adaptation. .